1. Field of the Invention
The invention relates to a common rail for a common rail fuel injection system of an internal combustion engine, having a tubular base body whose interior communicates with a plurality of connections.
2. Description of the Prior Art
In common rail injection systems, a high-pressure pump, optionally with the aid of a prefeed pump, pumps the fuel to be injected from a tank into the central high-pressure fuel reservoir, also known as a common rail. From the rail, fuel lines lead to the various injectors, which are assigned to the engine cylinders. The injectors are triggered individually by the engine electronics as a function of the engine operating parameters, in order to inject fuel into the engine combustion chamber. By means of the common rail, the pressure generation and the injection are decoupled from one another.
A conventional common rail is described for instance in German Patent Disclosure DE 195 48 611. The known common rail withstands pressures of up to about 1100 bar.
The object of the invention is to increase the high-pressure strength of the known common rail by simple provisions. Furthermore, the common rail of the invention should be economical to produce.
In a common rail for a common rail fuel injection system of an internal combustion engine, having a tubular base body whose interior communicates with a plurality of connections, this object is attained in that the interior is formed by at least two substantially circular-cylindrical recesses, which communicate with one another and whose longitudinal axes are parallel to one another, and in that the connections originate only at the jacket face of one of the substantially circular-cylindrical recesses. Within the context of the present invention, it has been found that the high-pressure strength of the common rail is limited primarily by the intersections between the connection openings and the base body interior. In operation, major forces act on the transitions between the connection openings and the base body. According to the present invention, the functions of storage and distribution of the base body interior are distributed between the two recesses. This makes it possible for the transitions that are especially critical with respect to high-pressure strength between the base body interior and the connection openings to be shaped optimally. Independently of the connections in the region of the jacket face of the circular-cylindrical recesses, connections can additionally be provided on the face ends of the circular-cylindrical recesses, because the intersection problems do not arise there.
A particular version of the invention is characterized in that the two substantially circular-cylindrical recesses communicate with one another through a connecting conduit. Separating the two circular-cylindrical recesses from one another means that pressure surges are not propagated from one circular-cylindrical recess to the other.
A further embodiment of the invention is characterized in that the two substantially circular-cylindrical recesses overlap in cross section. By means of the overlap, the available storage space is increased, without creating sharp edges that are critical with regard to the high-pressure strength.
A further version of the invention is characterized in that the two substantially circular-cylindrical recesses have the same diameters, and in that the connections are disposed only in the longitudinal direction of the cross section of the base body interior. The deformation seen in cross section, which is due to the high pressure prevailing in operation in the interior of the base body, is most pronounced perpendicular to the connections and thus occurs in a region that is not so heavily stressed.
A further version of the invention is characterized in that the two substantially circular-cylindrical recesses have different diameters, and in that the connections originate only at the jacket face of the substantially circular-cylindrical recess having the smaller diameter. As a result, the transition between the interior of the tubular base body and the connections is made less sharp, and the high-pressure strength of the common rail of the invention is improved.
A further version of the invention is characterized in that the spacing between the longitudinal axes of the two substantially circular-cylindrical recesses is greater than or equal to the radius of the substantially circular-cylindrical recess having the larger diameter. It is thus attained that the storage volume of the common rail of the invention is increased.
A further version of the invention is characterized in that the transitions between the two substantially circular-cylindrical recesses are rounded in cross section. The additional rounding leads to a further increase in the high-pressure strength of the common rail of the invention.